let audio_c = document.getElementById("audio_c");
let audio = document.getElementById("audio");
let onOff = true
audio_c.onclick = function () {
    if (onOff) {
        audio_c.src = "../images/audio-off.png";
        audio.pause();
        onOff = false;
    } else {
        audio_c.src = "../images/audio-on.png";
        audio.play();
        onOff = true;
    }
}